> The question I keep asking myself is, dollars aside, will solar cell X > produce enough energy in it's useful life to fabricate a duplicate of > itself. I don't believe I've found a "yes" yet... As I recall his point, Bob addressed this by suggesting that the retail cost of a product in a competitive market tends towards being its energy cost. That has merit, although there will be a scale factor in there. For order of cost figurings I find that the factory door cost of something from China approaches its material cost. That would vary for something with a high degree of complexity or "IP" content. Running those two together one is really saying that the invisible hand tends to sell things for around what they cost after having figured in energy, materials (with their own energy content), transportation, need to provide some holidays for the workers so they are more productive than otherwise etc. If somebody tries to sell things for more than the hand does then the hand will undercut them. If somebody sells for less them they will go broke or have already done so and are fire-sale-ing. [Note that I am not commenting on whether the hand does "best" or whether it should be allowed to do what it does or encouraged or discouraged from doing so - just what happens. In the case of PV panels, the cost seems to be far lower than I'd expect. At 4 hours/day mean full sun x 24 year lifetime (common enough now). 8765 hours/ year x 4/24 per day x 24 years each Watt of panel capacity makes about 35 kWh of energy. Cost that at 20 cents /unit (cheap in some markets, not so cheap in others) - $7 of energy over it's lifetime. Even at wholesale bulk generation energy rates of say 5 cents/unit that's $1.75. Discounted cash flow will bite into that savagely. This for laminated PV panels which cost $US0.65/Watt with low iron glass + EVA+Si-cells (incl bus and soldering & ...) + EVA + tedlar etc backsheet + Al frame + junction box + labor all ready to ship. That's frighteningly cheap. The Si component alone is presumably under 30 cents US/Watt bare. Given that $US0.65/Watt is the price at which people are happy with and will sell in unlimited volume and that nobody is giving them vast subsidies at this level (some subsidies, yes) then it must [tm] be comfortably (or somewhat) above the energy cost. So , as they make $7 retail =3D 10 x their factory door cost over a lifetime - even with due allowance for DCF they are "clearly" [[tm] again] easily covering their energy costs. Better yet - add the cost of shipping (about 10 cents/Watt?) mounting, maintenance etc and they are still probably making $ wrt energy cost. We seem to be beating the "inevitable decline which will occur after peak oil" :-). Adding batteries, mounting, reticulation, controllers, accommodation, maintenance, ... does rather make it all less attractive. Solar PV based powerstations are being built. With optimum choice of site, and such subsidies as they may manage they do not stand out head and shoulders over alternative more conventional means of producing grid electricity. ie we have just about almost reached grid parity in good cases downhill with the wind behind you. And that with the whole world's PV makers going to the wall due to utter lack of margins - certainly including the majority of Chinese PV manufacturers. We evidently need to learn a few more hydrocarbon lessons before we are ready for solar on a genuinely useful scale. Shame. If you can manage truly low cost installations and/or grid energy is very dear or unavailable then PV has "arrived". Battery costs would start to matter muchly. Over the lifetime of an installation LiFePO4 and new variants thereof may offer the lowest costs. Russell --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .